Late Monday afternoon, Senate Majority Leader Mitch McConnell will force the fourth vote in three weeks on a bill to fund the massive agency that protects Americans from terrorists, floods and incursions across the borders. Senate Democrats will almost certainly block it again.

And after that, all of McConnell’s options become messy, with just four days left to avoid a partial government shutdown that some senior GOP lawmakers and aides now consider nearly unavoidable.

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The Kentucky Republican could cave to Democrats’ demands and abandon the GOP’s attempt to tie the Department of Homeland Security’s funding to an attack on President Barack Obama’s immigration policies. But pushing through a short-term continuing resolution for DHS would bring howls from the right, postpone the immigration showdown for only a couple of weeks or months, and most likely fail in the House. McConnell would gain nothing even if he could pass such a CR, which is far from a sure thing.

Or, as some conservatives outside the Senate want, McConnell could employ the “nuclear option” to abolish the filibuster on legislation, allowing Republicans to pass the $39.7 billion DHS bill with a simple majority of 51 votes, rather than 60. But that would mean destroying the Senate traditions he’s vowed so loudly over the years to protect — and Obama would still veto the bill.

Or McConnell could keep bringing the same House-passed GOP bill up for more votes, seeking to break the filibuster, or hope Democrats will reach for a deal before the clock runs out at midnight Friday. But Obama’s party, convinced that voters will blame Republicans if DHS shuts down, is clearly relishing having the upper hand. The president is traveling to Miami on Wednesday for an immigration-related event to be broadcast on MSNBC, essentially goading conservatives to keep pushing for a shutdown over the issue — a move that one Senate GOP insider likened to throwing a “can of gasoline” on the fire.

McConnell, known for keeping even his inner circle in the dark about his thinking, isn’t tipping his hand so far on what he’ll do past Monday. No announcements are expected before Tuesday afternoon, when Senate Republicans and Democrats will huddle behind closed doors at their regularly scheduled policy luncheons.

But the upshot is this: Less than two months after taking charge of the Senate and vowing to avoid shutdowns, McConnell may be about to preside over the second one in 18 months for the sprawling DHS. That would send 30,000 employees home immediately and force 200,000 more to toil without paychecks until the impasse is cleared — potentially a huge blow to what Republicans had billed as their New American Congress.

Polls indicate that Republicans would take more of the blame for a DHS shutdown than Obama and the Democrats. With control of the Senate up for grabs in 2016, it’s not a path McConnell will want to take. Yet it’s not at all clear how he can avoid it. And he’s not getting much public help from Speaker John Boehner (R-Ohio), who says the House has done its part to pass a DHS bill and that it’s up to the Senate to do something.

One GOP strategy is to try to shift the blame to the Democrats for their repeated filibusters, pointing out that Obama’s party refuses to even debate changes to the Homeland Security bill.

“The only thing I would point out is that the only way we can amend the bill is if we get on it,” said Don Stewart, McConnell’s spokesman. “So far, Democrats haven’t chosen to do that.”

When asked what McConnell would do following Monday’s vote, Stewart said the GOP leader “is hoping Democrats will start the process” of seeking a way out of the standoff.

But Senate Democrats — with Obama’s blessing — have few incentives to yield. Either Republicans give up their fight to undo the executive actions in which Obama eased the deportation threat for several million undocumented immigrants — a move that would be anathema to the conservative base — or the shutdown plays to the Democratic argument that the GOP is not serious about governing.